1. Field of the Invention
The present invention relates to a control apparatus for controlling the amount of air to be taken into an engine by electronically driving a control valve.
2. Description of the Related Art
Instead of the conventional method of directly controlling a control valve (throttle valve) by means of an operation of an accelerator pedal, a method is now used in an air flow rate control apparatus such that a position (opening degree) of the control valve is controlled by an actuator such as a motor in accordance with the operating status of an engine on a vehicle so that an optimal air intake can be obtained.
In such technology, an output associated with the operating status, for example an output from an accelerator sensor for detecting the extent of depression of the accelerator pedal is processed to set or determine a target (desired) opening degree of the control valve. A control signal is then sent to an actuator such as a motor to drive the throttle valve. Further, a throttle sensor for detecting the opening degree of the throttle valve is provided. Until its output value becomes equal to a value corresponding to the target opening degree of the control valve, a feedback control on the control valve is continued (Japanese Patent Laid-Open Publication No. 61-8441).
In recent years, there is a trend of integrating and incorporating the types of control such as ISC (idle speed control), FICD (fast idle control) into an electric air flow rate control apparatus, which had conventionally been performed by separate component parts.
In order to achieve this, it is required to reduce mechanical hysteresis and electrical hysteresis possessed by the electric air flow rate control apparatus and to improve the resolution of a potentiometer or the like which serves as a throttle sensor for detecting the position of the control valve.
Further, connectors for electrical wiring are respectively provided for the actuator such as a motor provided to control the position (opening degree) of the control valve (throttle valve) and for the position detecting means therefor, resulting in a problem that the number of the connectors becomes large.